Idk, I'm inclined to think Hussie was giving trans topics serious thought as early as Problem Sleuth, even if the whimsical tone makes it difficult to recognize as such. Like the bit on page 583 where Nervous Broad (Pickle Inspector's feminine alter-ego) essentially looks into the mirror and sees herself as a monster struck me as a particularly melancholy nod to dysphoria, in the context of the story's various nods to body image issues (eg AD recalling being bullied for his weight, NB being self-conscious about her thin frame)